My kids have been collecting those for years. I think McDonald's has something they do in this area, they redeem them for cash. I've never seen it happen, but places like the daycare where my children used to stay always collected them. There are still a few sandwich baggies with the tabs around here. As suggested, it's the "rocker" thingie that pushes open the can (remember how people used to either litter the old pull tabs or drop them into the can? I'm sure more than a few people hurt themselves swallowing those things, and even more people complained about the litter).